In the DNA of a group of 5,000-year-old skeletons from Germany, they discovered no trace of the lactase allele, even though it had originated a good 3,000 years beforehand. Similar tests done on 3,000-year-old skeletons from Ukraine showed a 30 percent frequency of the allele. In the modern populations of both locales, the frequency is around 90 percent.
I thought I was on top of the literature, but this was new to me. It’s even more proof that human evolution did not stop with the advent of Homo sapiens. It has continued … even after the transition from prehistory to history!
The same article also has some thoughts from Bruce Lahn, the evolutionary geneticist who has mapped human variation at two genes, ASPM and microcephalin, that seem to regulate the growth of brain tissue.
Even if Lahn could prove to everyone's satisfaction that ASPM and microcephalin are under selection, whether intelligence is the trait being selected for would be far from a settled question. It could be, as Lahn suggested, that some other mental trait is being selected, or that the activity of ASPM and microcephalin in other parts of the body is what is under selection. More work will certainly be done. But one can speculate with far more confidence about what drove the dramatic increase in intelligence attested by the fossil record: the advent of human culture.
"Intelligence builds on top of intelligence," says Lahn. "[Culture] creates a stringent selection regime for enhanced intelligence. This is a positive feedback loop, I would think." Increasing intelligence increases the complexity of culture, which pressures intelligence levels to rise, which creates a more complex culture, and so on. Culture is not an escape from conditioning environments. It is an environment of a different kind.
Reference
Phelan, B. (2008). How we evolve. A growing number of scientists argue that human culture itself has become the foremost agent of biological change. Seed Posted October 7, 2008
'"Intelligence builds on top of intelligence," says Lahn. "[Culture] creates a stringent selection regime for enhanced intelligence. This is a positive feedback loop, I would think." Increasing intelligence increases the complexity of culture, which pressures intelligence levels to rise, which creates a more complex culture, and so on.'
ReplyDeleteUp until the advent of contraception, he should say. That was the big game changer.
Are you rediscovering "lamarckism" ?
ReplyDeleteGive proper credit to Sir de-Lamarck please, as his hypothesis were formulated in a time where genes were unknown, during the french revolution 200 years ago.
The reason Lamarckism is banned from being mention is political.
Remember that him and Darwin were speaking at the time of a revolution, political in France and technical all over Europe.
Darwin says that if you are a poor kid and work in a coil mine in Walles, that's too bad, because of you genes, but somehow, everything is right and everybody is in his place. You've done the best you could do with the genes given to you (inherited from your worthless parent).
Lamarck said that perhaps by working hard, you can overcome your genes by fighting them, over the generations. if you or your offspring are being predated, there is no fatality in that and you can change it, against your genes. Somehow there is an Intelligent Designer, and this is yourself.
So, gene-culture co-evolution is certainly not new, but be aware of the explosive content of this concept. It certainley desn't fit well in a society ruled by market capitalism and liberal consumerism.
Here is what say wiki about Lamarck:
"Lamarck's contribution to evolutionary theory consisted of the first truly cohesive theory of evolution, in which an alchemical complexifying force drove organisms up a ladder of complexity, and a second environmental force adapted them to local environments through "use and disuse" of characteristics, differentiating them from other organisms.[5]"
= gene culture co-evolution
RG
Coginitive performance if not intelligence will be increased by parental investment, this will often entail having fewer children so lower birthrates in high SES people might be increasing IQ. Low birth order children are said to surpass high birth order children intellectually and there may be a biological advantage in addition to the increased investment for the child, especially in sons.
ReplyDeleteAssortative mating is certainly increasing IQ. If the highest SES people are choosing each other to have children with and giving these offspring the the benefit of high investment parenting, which probably increases the chance that they will go on to assortively mate, then they are going rachet up their intelligence.
So culture might well be having the same effect as always at the upper end of IQ. At the lower end of it the idea of escaping from an enviroment's selection for 'improvment' in the intelectual sense might have some validity. Homo heidelbergenis manufactured throwing spears and possibly shelters but the Neanderthals who evolved from them couldn't do either. The effect of the cultural enviroment on the lowest SES might be to select 'for' something other than IQ, the opposite of it in fact.
RG, Lahn said:
ReplyDelete"Intelligence builds on top of intelligence," says Lahn. "[Culture] creates a stringent selection regime for enhanced intelligence."
Nothing Lamarckian about that.
Current generation poor and stupid will still have stupid children should they become rich (via AA, for example). But if, for some reason, they can't have children, like being too poor to attract a mate, for example, the gene pool increases in potential.
Affirmative Action : yesterday in the Dallas Morning News was an article about a new test evaluation system for kids, "who will be evaluated according to ethnicity and social background".
ReplyDeleteAnyway, I believe in gene culture co-evolution but I think it implies some lamarckian selection.
I don't say pure lamarckian, but some proportion of it, like chemicals bond are rarely purely covalent or purely ionic in nature, but a mixture of the two. Evolution mechanisms, in my opinion, can also be a mixture of Darwinian + Lamarckian forces. However, Lamarckian evolutionary drive needs a big information processor (a brain) because it is not transmitted by genes but by behavior or culture. Low level organisms such are bacterias can only treat information trough their genome: if they survive, the information in the genome is evaluated as good and is kept, if they don't survive the information is also evaluated as negative and discarded. In this case, the genome carries all the information. The only evolutionary driving force is Darwinian, which is nothing else than the processing of infomation trhough genes.
But all mammals have a brain which increases their information processing power and allows the lamarckian/cultural component to increase as well.
Have you seen this documentary of tigers introduced in South African reserves ? On their own, tigers teach new hunting techniques to new tigers born in the reserve, like hunting in pack, whih they don't do in Asia. Their new african prey are faster and run in open grass land, but tigers didn't have to run faster or anything like that, they just changed their techniques to an elaborate pack hunting with tigers pushing the crazy fast preys into the paws of stalking tigers.
There is few darwinian selection involved at the genetic level in this process, and future paleotonlogists would be puzzled to explain how tigers adaped to faster prey environnment without becoming faster themselves. In fact, slower tigers would survive as well or better than faster one, providing they are smart enough to understand the new techniques and teach it to their offsprings.
In this case, the information was not hereditary transmitted by genes, but hereditary transmitted through culture.
I would be curiuous to know what happened to these tigers, as their techniques were too good actually and they could kill, actually it was a massacre, too much preys with little energy spent in running, just barely a punch with their big paws. It was too easy for them. I would guess sexual selection and competition with lions is the next step for them.
RG
The Seed article was easy to follow and very informative.
ReplyDeletehttp://www.lclarck.edu/~senegal/family.htm.
"The Maternal Uncle, or nijaay in Walof"
"Among many groups in Senegal a prefered marriage for a man is to his nijaay's daughter"
Leherensuge: Polygynic bias in reproduction... but how?
(A Basque blogger is puzzled by Hammer et. al.)
Anon,
ReplyDeleteYes, it sounds a lot like Lamarckian evolution. With gene-culture co-evolution, humans are no longer passive objects of selection. They are active agents in creating their environment of selection pressures.
As I understand Lamarckism, the use or disuse of a particular organ, ability, etc. has a direct effect on the genome. Is this a misrepresentation of Lamarcke's thinking? Did he ever talk in terms of selection?
Tod,
When I read books on social history, I often come across statements to the effect that a prospective bride should come from "a good family". The idea was that a man should judge a woman not only by her own characteristics but also by those of her lineage. Did this reflect a belief in the genetic transmission of mental/behavioral characteristics?
Thanks for the references. The Basque blogger has an interesting website.
Lamarck did not know about the genome, but like Darwin, he knew about heredity.
ReplyDeleteHis point was that the use or disuse of an organ had an effect on heredity. "Acquired traits (through behavior) are transmitted", he said. Lamarck implicitly admits "behavior" as "Selection" in this process. This is clearly wrong if you say "Traits = information encoded in DNA" but can be true if you generalize the concept to Evolution = transmitted information to any support, RNA, DNA, proteins, behavior, etc.
But how could this "transmitted information" impact the genome ? : Possibly through epigenetic and transcriptome regulation.
It's possible that the fast evolutionoary rate that punctates the evolutionary stasis described by Gould, is driven by transcriptome response upon acquired behavior and that only after, these changes become fixed in the genome. In this sense the genomic DNA is just a hardware backup like a DVD. Although it is just a conjecture, Micro RNAs control the degradation of target messanger-RNAs of developmentaly regulated transcription factors and therefore they indirectly control developmental processes. Can they also affect DNA replication and recombination events during meiosis ?
We don't know yet but as studies on non coding transcriptome and other phenomena accumulate, I predict that more and more data will backup the idea that changes in the transcriptome can affects the evolution of the genome more than the opposite.
You will then have a serious support to the lamarckian concept that evolution of evolved species is partly "acquired information transmited through behavior, then through the transcriptome, then to the genome". Such an evolutionary process can be viable only in evolved species, such as birds and mammals but it does not exclude darwinian selection either.
As a matter of fact, Darwin nor Lamarck could know with certitude the origine of the changes they were observing.
Under the conjecture that lamarckian processes are part of species evolution, especially the most evolved, human genes (I guess mostly cognitive-related genes) and human cultures co-evolve together. And as i said earlyer, this has a consequence: there is an Intelligent Designer and this is Us.
RG
I think the rationale would be unspoken folk wisdom rather than conscious belief in genetics. The "of good family" caveat could even apply to things like regression to the mean for children of a low SES mother, genomic imprinting confict, or epigenetic infuences from grandparents.
ReplyDelete